Round balers generally have a bale forming chamber defined by a pair of opposing side walls associated with an array of side-by-side belts, transverse slats trained on chains, a plurality of transverse rolls or a combination of these various elements, e.g., rolls and belts. During field operation, windrowed crop material such as hay is picked up from the ground and fed in a continuous stream into a fixed or variable diameter chamber. The hay is rolled into a cylindrical package within the chamber, wrapped with twine, net or the like and ejected onto the ground for subsequent handling.
U.S. Pat. No. 5,289,672, issued Mar. 4, 1994 in the name of Kenneth R. Underhill, and, U.S. Pat. No. 4,956,968, issued Sep. 18, 1990, also in the name of Kenneth R. Underhill, disclose one type prior art round baler of the general nature described above. In this particular type of baler an expandable chamber is defined by a pair of fixed sidewalls, and a plurality of side-by-side belts cooperating with a series of transverse rolls, mounted between a pair of pivotally mounted arms. This arrangement of rolls and arms is commonly referred to as a sledge assembly. The chamber includes an inlet opening in the front through which crop material is fed. Also included is a pair of take up arms pivotally mounted on the main frame, between which arms a pair of guide rolls are journalled. A biasing force on the take up arms urges the outer surfaces of the guide rolls against the belts to maintain tension and thereby prevent slack from occurring in the belts during expansion and contraction of the chamber. Density of the bale can be affected by varying the force on the take up arms.
Another type prior art round baler of the same general nature employs a plurality of transverse rollers to define a cylindrical bale forming chamber with a fixed diameter. Examples of this type baler are shown in U.S. Pat. No. 4,612,855, issued Sep. 23, 1986 in the name of Robert A. Wagstaff, et al, U.S. Pat. No. 4,604,848, Aug. 12, 1986 in the name of Gerhard Clostermeyer, and U.S. Pat. No. 4,841,851, issued Jun. 2, 1989 in the name of Pierre Quataert. It should be noted that the '851 patent shows additional embodiments wherein a fixed chamber is defined by means other than rolls, i.e., belts (FIG. 7) or chains and slats (FIG. 8).
The present invention relates to a wrapping system for a round baler in which a cylindrical package of crop material is formed in a fixed or expanding chamber wherein one or more transverse forming rollers are employed. For example, the chamber could comprise fixed side walls and expandable transverse elements consisting of a combination of belts and rolls of the general nature described in the '672 patent, cited above. This is one example of the many prior art patents assigned to the assignee, New Holland North America, Inc., that disclose this type of expandable chamber round baler. It is not uncommon in prior art round balers having this general configuration to feed the wrapping material between a pair of transverse rollers. Alternatively, the chamber could comprise fixed side walls and transverse elements at fixed locations in a configuration of the general nature described in the '855 patent, cited above.
Unique characteristics of the present invention, described below, contribute to a wrapping system for round balers that consistently introduces wrapping material to the periphery of the cylindrical package formed in the chamber regardless of whether the diameter of the chamber is fixed or variable, and regardless of the nature of the transverse wall, i.e., belts, rolls or chains.
The present invention relates to several features of wrapping apparatus for round balers of the general nature described in the preceding paragraph. These unique features, described below, contribute to improved performance and operability of round balers. Additionally, these features are consistent with lower manufacturing costs without detracting from simplicity of field operation and serviceability.